[v6,13/24] mm: Introduce __maybe_mkwrite()

Message ID 1515777968-867-14-git-send-email-ldufour@linux.vnet.ibm.com
State Not Applicable
Headers show
  • Speculative page faults
Related show

Commit Message

Laurent Dufour Jan. 12, 2018, 5:25 p.m.
The current maybe_mkwrite() is getting passed the pointer to the vma
structure to fetch the vm_flags field.

When dealing with the speculative page fault handler, it will be better to
rely on the cached vm_flags value stored in the vm_fault structure.

This patch introduce a __maybe_mkwrite() service which can be called by
passing the value of the vm_flags field.

There is no change functional changes expected for the other callers of

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
 include/linux/mm.h | 9 +++++++--
 mm/memory.c        | 6 +++---
 2 files changed, 10 insertions(+), 5 deletions(-)


diff --git a/include/linux/mm.h b/include/linux/mm.h
index f14a73a8d420..d77a11067b94 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -685,13 +685,18 @@  void free_compound_page(struct page *page);
  * pte_mkwrite.  But get_user_pages can cause write faults for mappings
  * that do not have writing enabled, when used by access_process_vm.
-static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+static inline pte_t __maybe_mkwrite(pte_t pte, unsigned long vma_flags)
-	if (likely(vma->vm_flags & VM_WRITE))
+	if (likely(vma_flags & VM_WRITE))
 		pte = pte_mkwrite(pte);
 	return pte;
+static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
+	return __maybe_mkwrite(pte, vma->vm_flags);
 int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
 		struct page *page);
 int finish_fault(struct vm_fault *vmf);
diff --git a/mm/memory.c b/mm/memory.c
index cbd7e5c3a42f..c24891d5676f 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2438,7 +2438,7 @@  static inline void wp_page_reuse(struct vm_fault *vmf)
 	flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
 	entry = pte_mkyoung(vmf->orig_pte);
-	entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+	entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
 	if (ptep_set_access_flags(vma, vmf->address, vmf->pte, entry, 1))
 		update_mmu_cache(vma, vmf->address, vmf->pte);
 	pte_unmap_unlock(vmf->pte, vmf->ptl);
@@ -2529,8 +2529,8 @@  static int wp_page_copy(struct vm_fault *vmf)
 			inc_mm_counter_fast(mm, MM_ANONPAGES);
 		flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
-		entry = mk_pte(new_page, vma->vm_page_prot);
-		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+		entry = mk_pte(new_page, vmf->vma_page_prot);
+		entry = __maybe_mkwrite(pte_mkdirty(entry), vmf->vma_flags);
 		 * Clear the pte entry and flush it first, before updating the
 		 * pte with the new entry. This will avoid a race condition